1. Field of the Invention
The invention relates to a digital telecommunication system in which each terminal communicates via a base station also referred to as a connection station. It also relates to a method of allocating communication resources in a digital telecommunication system in which each terminal communicates via a base station also referred to as a connection station and to a terminal and means for managing the system.
2. Description of the Prior Art
Telecommunication systems such as mobile telephone systems and satellite telecommunication systems are based on dividing a territory into geographical areas.
In the case of a mobile telephone system, the geographical areas are generally referred to as cells and their dimensions vary according to their location, being small in an urban area and larger in a rural area. In a mobile telephone system the terminals, in other words the mobile transmitters and receivers, communicate with each other or with terminals of other networks via a base station provided in each area.
In the case of a geosynchronous or non-geosynchronous satellite telecommunication system, at least a major part of the Earth is divided into areas each of which has a diameter of the order of several hundred kilometers and the fixed or mobile terminals communicate via a connection station, also referred to as a management station, in that area, calls being relayed by equipment on board a satellite.
In geosynchronous and non-geosynchronous satellite telecommunication systems, the information transmitted is in digital form and is grouped into cells, also referred to as packets, that conform to the ATM standard, for example.
Each area is allocated communication resources consisting of frequencies and/or codes. If terminals are communicating simultaneously with the base station or connection station separate resources are allocated to each terminal to prevent interference between terminals transmitting simultaneously and so that the station can determine the origin of the cells or packets. In addition to frequencies and/or codes, the resources generally include a time position for each cell or packet. It is therefore necessary to provide a centralized resource management unit in each area whose function is to allocate communication resources to each terminal.
If each terminal can send and receive information of different types, that is to say having different qualities of service, the central management unit allocates resources to each terminal according to its quality of service. If a terminal can set up several connections simultaneously, resources are allocated to each connection.
For the central management unit to be able to know the requirements of each terminal, and possibly of each connection, the terminals must send it signaling information.
If the calls are in circuit-switched mode, that is to say if resources are allocated when a connection is set up, the quantity of information to be transmitted to the management unit remains moderate.
However, it is preferable for the resources to be allocated cell by cell or packet by packet to optimize the distribution of resources at any given time. In this case, the signaling information transmitted from the terminals to the management unit is voluminous. Also, the greater the number of connections and qualities of service per terminal, the greater the quantity of signaling.
The invention provides a system and a method for minimizing the signaling necessary for allocating resources.
In the above telecommunication systems the methods for allocating resources used until now cannot correctly isolate the flows of data between terminals, sporadic traffic in some terminals having an effect on the continuous traffic of other terminals, for example. Also, the prior art methods cannot always distribute communication resources equitably between the terminals and jitter between the incoming and outgoing flows can be prohibitive. The term “jitter” refers to the accuracy of the time at which the flows to be transmitted are transmitted. If that accuracy is not sufficient, the transmission of some data is interfered with, for example real time video transmission.
Another aspect of the invention ensures correct isolation between flows from different terminals, equitable distribution of resources between terminals and low jitter on transmission.